1. Field of the Invention
The present invention relates to a method for packaging carbon dioxide snow in plastic bags.
2. Description of the Related Art
It is known that frozen or deep-frozen products, particularly food products which have to be kept at low temperature (of the order of xe2x88x9220xc2x0 C. or under) with uninterrupted coldness from the time they are frozen or deep-frozen to the time of their use, require warehouses, transport facilities and stores fitted with refrigeration equipment, which at the present time is generally electrical. However, in many instances, for example for non-motorized transport, it is impossible to transport the products without taking them out of the refrigeration equipment in which they are stored, and the risk of the temperature rising is great if the weather conditions are unfavourable. With a view to avoiding such a temperature rise when they are being transported, it is common practice for the frozen or deep-frozen products to be placed in a dry ice (carbon dioxide ice) environment, the ice being procured for the party acquiring the products by the distributor of the products, generally free of charge. A certain misconception over cooling techniques on the part of the distributors and of the clients causes them usually to deliberately overestimate, as a precautionary measure, the amount of ice needed, and this results in significantly needless expenditure on the part of the distributor. In consequence, it has been proposed that carbon dioxide ice be replaced by carbon dioxide snow which is a relatively inexpensive product with a better cooling capability, its temperature of around xe2x88x9280xc2x0 C. allowing the products to be kept cold for longer. Thus, application FR-A1-2 604 243 describes the dispensing of carbon dioxide snow into bags, boxes or containers that are to be placed with the products to be preserved. That application describes an apparatus for bagging carbon dioxide snow, comprising:
means for continuously dispensing a porous flexible strip,
means for shaping into a tube the strip which is forced through a pre-shaping sheath,
a pipe for injecting liquid carbon dioxide anhydride, this pipe being arranged in the tube upstream of the preshaping sheath,
a driving and shaping set arranged downstream of the reshaping sheath and acting on the tube filled with carbon dioxide snow,
a station for cutting the tube and the solidified carbon dioxide snow.
When this type of bagging apparatus is used with a plastic film, a problem of closing the plastic tube is encountered. This is because it has been found that when the carbon dioxide snow, which is in pulverulent form as it leaves the carbon dioxide snow generator, is introduced into the plastic tube, particles of snow tend to be sent back to the generator. Numerous snow particles therefore remain in the space between the two edges of the film which are intended to be hot-welded together. The presence of this solid at xe2x88x9280xc2x0 C. at the hot-welding jaws prevents effective closure of the bag. This phenomenon is all the more pronounced when the apparatus has not been operating for a certain period of time, for example for about half an hour or upon start-up.
The object of the present invention is to propose an apparatus for bagging carbon dioxide snow into plastic bags which does not exhibit the above problem.
To this end, the invention relates to a method for packaging carbon dioxide snow in a plastic film container, in which method the following steps are employed:
axe2x80x94a fluid which has a temperature below the dew point of the air is injected into and in contact with the plastic film container, then
bxe2x80x94the carbon dioxide snow is introduced into the plastic film container, then
cxe2x80x94the plastic film container is closed.
The invention also relates to a device for packaging carbon dioxide snow in plastic film, comprising:
xe2x80x94means for dispensing and shaping the plastic film,
xe2x80x94a source of liquid carbon dioxide,
xe2x80x94a means for injecting a fluid which has a temperature below the dew point of air into and in contact with the shaped plastic film,
xe2x80x94a carbon dioxide snow generator connected to the source of liquid carbon dioxide and positioned in such a way to fill the shaped plastic film,
xe2x80x94means for sealing the shaped plastic film.